When a group of missionary aid workers in Myanmar disappear into the vast green inferno, vigilante Vietnam War veteran John Rambo leaves his job as a Salween River boatman behind to accompany a group of mercenaries on a daring rescue mission. It's been twenty years since Rambo helped mujahedeen rebels fend off Soviet invaders in Afghanistan, and these days the former soldier lives a simple life in northern Thailand. But it's time now for Rambo to take up arms once more and mete out his own, unique, brand of justice.